Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
map = [ list(input()) for _ in range(h) ]
ans = 0
for i in range(h):
    l = map[i]
    ans += l.count(".")

def bfs(x, y):
    for (next_x, next_y) in [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]:
        if 0 <= next_x < h and 0 <= next_y < w and map[next_x][next_y] == ".":
            map[next_x][next_y] = 1 + map[x][y]
            q.append([next_x, next_y])

map[0][0] = 1
q = deque([[0, 0]])
while True:
    if len(q) == 0:
        break
    x, y = q.popleft()
    bfs(x, y)

if map[h-1][w-1] == ".":
    ans = -1
else:
    ans -= map[h-1][w-1]

print(ans)